JP2011245524A - Method for manufacturing helical gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a helical gear with high accuracy without causing an under-fill at a side for starting tooth molding and without causing a swelling part at a side for finishing the tooth molding.SOLUTION: The forging molding method of the helical gear forms a helical tooth part 23 at an outer circumference of a preformed gear W3 by allowing the preformed gear W3 to be press-fitted in a tooth profile of a die from one end side. In the outer diameter of the preformed gear W3, one end side 12a in an axial direction where tooth part molding is started by being press-fitted in the tooth profile of the die first is formed to be larger in a diameter than the other end side 12b in the axial direction where the tooth part molding is finished.

Description

  The present invention relates to a method for forging a helical gear having a helical tooth profile formed on its outer periphery.

Conventionally, when forming helical gears with helical teeth on the outer periphery, after forging a disk-shaped or ring-shaped forged product from the material in advance, the helical teeth are formed on the outer periphery of the forged product by cutting such as gear shaving or hob. Many have been practiced to form helical gears.

However, when cutting is performed, a cost increase due to an increase in the number of processes and a long manufacturing time are required. Therefore, a method for forming helical teeth by forging is required. As a method, the material of the helical gear is arranged in the die of the forging device, the punch is pushed in from one side of the die and pressed from one end side of the material, and at the same time, pressed from the other end side by another punch, There has been proposed a method in which helical teeth are formed by passing through a tooth forming portion of a die while a material is sandwiched between two punches (see Patent Document 1).

JP 62-28040 A

  By the way, in the helical gear, since the teeth are inclined, the resistance increases with the progress of the tooth forming, and an event occurs in which the load applied to the other end in the axial direction where the tooth portion forming ends is gradually increased. Then, as in the helical gear W104 shown in FIG. 7, the thinning occurs at the tooth tip of the helical tooth portion 121 on the axial one end 112a side where the tooth portion forming is started. Further, a bulging portion that bulges from a desired diameter is formed on the side of the other axial end 112b where the tooth formation is completed.

  Even in the molding method described in Patent Document 1, a tooth shape is formed by pressing a cylindrical gear material with a pressure punch and passing through a tooth forming portion of a die. Since the resistance gradually increases from the other end side toward the one end side, it is conceivable that a lack of thickness is generated at the tooth tip on the one end side.

  The present invention has been made in view of the above circumstances, and in a forging method of a helical gear in which a preliminary gear is press-fitted from one end side into a die formed with a tooth profile portion to form a helical tooth portion on the outer periphery of the preliminary gear. Highly accurate helical teeth are formed without forming a thin wall on one axial end side where part molding is started, and without generating a bulging part on the other axial end side where tooth molding is finished. An object of the present invention is to provide a method for manufacturing a helical gear.

  The helical gear manufacturing method of the present invention is a helical gear forging method in which a helical gear is formed on the outer periphery of the spare gear by press-fitting the spare gear into one end of the die from one end side. The first feature is that one end side in the axial direction where the tooth part molding is started by press-fitting into the tooth profile part of the die is formed to have a larger diameter than the other axial end side where the tooth part molding is finished.

  The helical gear manufacturing method of the present invention has a second feature that the outer peripheral shape of the spare gear is formed by cutting.

  The helical gear manufacturing method of the present invention includes a first forming step in which a spare gear is press-fitted into a die from one axial end side to form a helical tooth portion on the outer periphery, and a spare gear shaft having a helical tooth portion formed on the outer periphery. And a second forming step of pressing the end surface on the one end side with a punch arranged on the inner periphery of the die.

  The helical gear manufacturing method of the present invention includes a first tooth portion on which a helical tooth portion is formed, and a second large diameter portion that is continuous from the first tooth portion and is larger in diameter than the outer diameter of the first tooth portion. The fourth feature is that the helical gear is forged.

  According to the helical gear manufacturing method of the first feature of the present invention, in the helical gear forging method of forming the helical gear on the outer periphery of the spare gear by press-fitting the spare gear from one end side into the tooth profile of the die, The outer diameter of the spare gear is formed so that the one end side in the axial direction where the tooth part forming is started by first press-fitting into the tooth profile part of the die is larger than the other end side in the axial direction where the tooth part forming ends. Even if the load applied to the tooth forming planned part from the part forming start side gradually increases, the other end in the axial direction on the tooth forming end side has a small diameter in advance, so even if a lot of meat flows, it bulges larger than the desired tooth tip diameter Can be prevented. Moreover, since it is formed in large diameter in advance in the axial direction one end side which is a tooth tip shaping | molding start side, it can prevent that a flesh flows to a tooth tip and a lack of thickness arises.

  According to the helical gear manufacturing method of the second feature of the present invention, since the outer peripheral shape of the spare gear is formed by cutting, the outer peripheral shape can be formed into a desired shape.

  According to the helical gear manufacturing method of the third feature of the present invention, the first gear is formed by press-fitting the spare gear into the die from one end side in the axial direction to form teeth on the outer periphery, and the helical tooth portion is formed on the outer periphery. And the second molding step of pressing the end surface of the auxiliary gear in the axial direction with a punch arranged on the inner periphery of the die, the teeth formed in the first molding step can be further expanded into the tooth profile portion, It is possible to form a helical tooth portion with higher tooth tip accuracy.

  According to the helical gear manufacturing method of the fourth aspect of the present invention, the first tooth portion on which the helical tooth portion is formed, and the first tooth portion continuous from the first tooth portion and having a diameter larger than the outer diameter of the first tooth portion. Since the helical gear with two large-diameter parts is forged, the first tooth cannot be sealed when forming the helical tooth, but it bulges to the other end in the axial direction where the tooth is formed The helical tooth portion of the first tooth portion can be forged and formed without generating a portion.

It is a cross-sectional top view showing the manufacturing process of the helical gear of this invention. It is a principal part enlarged view of the spare gear of this invention. It is a partial cross-sectional top view showing the process of forging a helical tooth part on the outer periphery of the spare gear of the present invention, the left side before forming the spare gear, and the right side showing during molding. It is a cross-sectional top view showing the state before shape | molding a helical gear in the spare gear of this invention. It is a cross-sectional top view showing the state of the 1st process in the forge molding process of the preliminary gear of this invention. It is a cross-sectional top view showing the state of the 2nd process in the forge forming process of the preliminary gear of this invention. It is a cross-sectional top view showing the helical gear manufactured with the conventional shaping | molding method.

  Embodiments of the present invention will be described below on the basis of preferred embodiments of the present invention shown in the accompanying drawings.

  First, the forming process of the helical gear W4 in the present invention will be described based on FIG. By pressing the cylindrical material obtained by cutting the wire into a required length in the axial direction, the disk-shaped material W0 is hot forged as shown in FIG. Next, as shown in FIG. 1A, the material W0 has a spare large-diameter portion 1 having an opening 3 on one side and an outer diameter that is continuous from the spare large-diameter portion 1 and smaller than the spare large-diameter portion 1. A preliminary shape material W1 including the preliminary small diameter portion 2 formed with the bottom portion 4 for closing the other bottom is formed by hot forging. Next, the bottom portion 4 of the preliminary shape material W1 is punched, and a preliminary shape gear W2 having a through hole 17 is formed as shown in FIG. Next, as shown in FIG. 1D, the outer peripheral surface of the preliminary small-diameter portion 2 of the preliminary-shaped gear W2 has a smaller diameter on the axial other end 12b side than the axial one end 12a side by cutting with a lathe. Thus, the small-diameter portion 12 is formed, and the spare gear W3 is formed. Finally, as shown in FIG. 1 (o), a helical-shaped helical tooth portion 21 is formed on the outer peripheral surface of the small-diameter portion 12 of the preliminary gear W3 by cold forging, and the helical tooth portion 21 is formed. A helical gear W4 including a single tooth portion 23 and a second large diameter portion 22 having an outer diameter larger than that of the first tooth portion 23 is formed.

  The preliminary gear W3 shown in FIG. 1D will be described in more detail. The spare gear W3 includes a small diameter portion 12, a large diameter portion 11 having an outer diameter larger than that of the small diameter portion 12, and a step portion 13 connecting the small diameter portion 12 and the large diameter portion 11. The small diameter portion 12 has a larger outer diameter on the axial end 12a side than the axial other end 12b continuous from the step portion 13, and as shown in FIG. 2, the axial direction extends from the axial end 12a to the axial direction. A maximum diameter portion 12c extending straight toward the other end 12b side, a minimum diameter portion 12d extending straight from the other axial end 12b side toward the one axial end 12a and having an inner diameter smaller than the inner diameter of the maximum diameter portion 12c; It consists of a continuous portion 12e having a tapered shape that gently connects the maximum diameter portion 12c and the minimum diameter portion 12d. The outer diameter of the small diameter portion 12 is the largest diameter, and the outer diameter of the end portion on the axial end 12a side of the largest diameter portion 12c is the largest diameter portion of the tooth shape portion 76 of the die 73 described later. However, it may be the same as or smaller than the inner diameter of the tooth profile large diameter portion 76a. Further, the outer diameter of the minimum diameter portion 12 d of the small diameter portion 12 is formed larger than the inner diameter of the tooth profile small diameter portion 76 b which is the minimum diameter portion of the tooth profile portion 76. The helical gear W4 in which the helical tooth portion 21 is formed in the small diameter portion 12 further forms a spur tooth portion on the outer peripheral surface of the second large diameter portion 22, and becomes a sun gear used in the transmission mechanism.

  Next, a forging apparatus that forges the helical portion 21 on the outer peripheral surface of the small diameter portion 12 of the spare gear W3 will be described with reference to FIG.

  A forged product forming apparatus 51 shown in FIG. 3 includes a movable die 61 and a fixed die 71 that are arranged to face each other in the axial direction. The movable die 61 has a punch 62 having a through hole along the axis and a punch holder 66 for holding the punch 62. A mandrel 65 is disposed concentrically inside the punch 62. The mandrel 65 is formed so that its outer diameter is the same as the inner diameter of the small diameter portion 12 of the spare gear W3 or smaller than the inner diameter of the small diameter portion 12 of the spare gear W3. Further, the fixed die side end of the punch 62 has a first end portion 63 having a shape similar to the inner peripheral surface of the spare gear W3, and the other end surface in the axial direction of the spare gear W3, which is continuous from the first end portion 63. And a second end 64 that presses 14.

  The fixed die 71 has a die 73 having a tooth profile portion 76 for forming the helical tooth portion 21 of the helical gear W3 on the inner periphery, a counter punch 72 disposed on the inner periphery side of the die 73, and an inner periphery of the counter punch 72. And a knockout 77 to be arranged. The die 72 includes an upper die 74 and a lower die 75 on which the upper die 74 is placed. The upper die 72 has a tooth-shaped large-diameter portion 76a having an inner diameter smaller than the outer diameter of the small-diameter portion 12 of the spare gear W3 on the axial end 12a side, and a smaller diameter than the outer diameter of the straight portion 12b of the small-diameter portion 12 of the spare gear W3. A tooth profile portion 76 having a small diameter tooth profile portion 76b is formed, and a tapered guide portion 74a having a smaller diameter from the top to the bottom in the drawing is formed on the upper end surface. The lower die 75 is in contact with the pin 78, and the die 75 can be moved in the axial direction via the pin 78 by a hydraulic cylinder (not shown).

  Next, a method for forging the helical tooth portion 21 on the outer peripheral surface of the small diameter portion 12 of the spare gear W3 using the forging device 51 will be described.

  First, as shown in the left half part of FIG. 3 and FIG. 4, the spare gear W <b> 3 is placed on the guide part 74 a of the upper die 74. Subsequently, the punch 62 and the mandrel 65 are integrally lowered, and the mandrel 65 is inserted through the through hole 17 of the spare gear W3. Further, the punch 62 has a first end 63 having a shape similar to that of the spare gear W3 abuts on the inner peripheral surface of the spare gear W3, and at the same time the second end 63 abuts on the other end side end surface 14 of the spare gear W3. Further, it moves to the fixed mold 71 side. The preliminary gear W3 is moved into the upper die 74 by being pressed by the punch 62, and the outer peripheral surface of the small-diameter portion 12 of the preliminary gear W3 is within a tooth profile 76 formed on the inner peripheral surface of the upper die 74 as shown in FIG. The helical tooth portion 21 is formed on the outer peripheral surface of the small-diameter portion 12 of the preliminary gear W3.

  At the same time as the formation of the predetermined helical tooth portion 21 on the outer peripheral surface of the small diameter portion 12 of the preliminary gear W3, the outer peripheral step portion 13 connecting the small diameter portion 12 and the large diameter portion 11 of the preliminary gear W3 contacts the upper die 74. The punch 62 and the mandrel 65 continue to descend as a unit, and are pressed via the spare gear W3, so that the die 73 also begins to descend. Next, one end face 15 in the axial direction of the small-diameter portion 12 of the preliminary gear W3 comes into contact with the counter punch 72, and the preliminary gear W3 descends and is pressed against the counter punch 72 from below. As shown in the left half of FIG. 3 and FIG. 6, the forged meat of the small diameter portion 12 of the preliminary gear W <b> 3 flows to the outer peripheral side of the helical tooth portion 21 by the pressing of the counter punch 72.

  When the formation of the helical tooth portion 21 on the outer peripheral surface of the small-diameter portion 12 of the preliminary gear W3 is completed, the punch 62 and the mandrel 65 are retracted upward and the knockout 77 is lifted and comes into contact with the helical gear W3. 73 is taken out.

  As described above, according to the helical gear manufacturing method of the present invention, the helical gear forging method for forming the helical tooth portion on the outer periphery of the preliminary gear by press-fitting the preliminary gear into the tooth profile portion of the die from one axial end side. Therefore, the outer diameter of the auxiliary gear is formed so that the one end side in the axial direction where the tooth part molding is started by first press-fitting into the tooth profile part of the die is larger than the other end side in the axial direction where the tooth part molding is finished. Even if the load applied to the outer peripheral surface of the auxiliary gear from the one end side in the axial direction where the tooth part molding starts gradually increases, the other end side in the axial direction where the tooth part molding ends is smaller in diameter than the one end side in the axial direction. Even if it flows a lot, it can be prevented that it bulges larger than the desired tip diameter. Moreover, since it is previously formed in the large diameter also in the axial direction one end side where tooth | gear part shaping | molding starts, it can prevent that a forge meat flows to a tooth tip and a missing wall arises.

  Further, according to the helical gear manufacturing method of the present invention, the outer peripheral shape of the spare gear is formed by cutting, so that one end side in the axial direction where the tooth portion molding is started by first press-fitting into the tooth shape portion of the die is the tooth portion. It is possible to easily form a desired outer peripheral shape that is formed to have a larger diameter than the other end in the axial direction where the forming is completed.

  Furthermore, according to the helical gear manufacturing method of the present invention, a first forming step in which a spare gear is press-fitted into a die from one end side in the axial direction to form teeth on the outer periphery, and a spare gear having a helical tooth portion formed on the outer periphery. And a second molding step in which the end surface on the one end side in the axial direction is pressed with a punch disposed on the inner periphery of the die, so that the teeth formed in the first molding step can be further expanded into the tooth profile portion, A highly accurate helical tooth can be formed.

  Moreover, according to the helical gear manufacturing method of the present invention, the first tooth portion on which the helical tooth portion is formed, and the second large diameter portion that is continuous from the first tooth portion and is larger in diameter than the outer diameter of the first tooth portion. Forging a helical gear equipped with the above-mentioned, the first tooth portion cannot be sealed and formed at the time of forming the helical tooth portion, but a bulging portion is generated on the other axial end side where the tooth portion forming is completed. Without this, the helical tooth portion of the first tooth portion can be forged.

  In this embodiment, a first forming step of press-fitting a spare gear into a die from one end side in the axial direction and molding teeth on the outer periphery, and a second forming step of pressing the end surface on the one end side in the axial direction of the spare gear with a punch, However, even in the first step alone, since the other end side of the tooth forming end side has a small diameter in advance, even if a lot of forged meat flows, it is possible to prevent the bulge from being larger than the desired tooth tip diameter. it can. Also, it goes without saying that the helical gear can be formed without a lack of thickness even at one end side, which is the tooth forming start side.

  Further, in this embodiment, a helical gear having a first tooth portion on which a helical tooth portion is formed and a second large diameter portion that is continuous from the first tooth portion and is larger in diameter than the outer diameter of the first tooth portion. However, it is possible to form a helical gear that does not have the second large diameter portion.

  The helical gear is applied to a product that requires a high meshing rate, and the present manufacturing method can be applied to all gears having helical teeth formed on the outer periphery. A single-stage gear or a multi-stage gear used in a transmission mechanism can be applied.

DESCRIPTION OF SYMBOLS 11 Large diameter part 12 Small diameter part 12a Axial direction end 12b Axial direction other end 15 Axial direction one end face 21 Helical tooth part 22 Second large diameter part 23 First tooth part 63 Punch 73 Dies 76 Tooth shape part W3 Spare gear W4 Helical gear

Claims (4)

  In the forging method of the helical gear W4 in which the helical gear W3 is formed on the outer periphery of the preliminary gear W3 by press-fitting the preliminary gear W3 from the axial one end 12a side into the die 73 in which the tooth profile portion 76 is formed. The outer diameter of W3 is formed such that the axial one end 12a side where the tooth part molding is started by first press-fitting into the tooth profile part 76 of the die 73 is larger than the axial other end 12b side where the tooth part molding is finished. A method for forging a helical gear.   2. The helical gear forging method according to claim 1, wherein the outer peripheral shape of the preliminary gear W3 is formed by cutting.   The preliminary gear W3 is press-fitted into the die 73 from the axial one end 12a side to form a helical tooth portion 21 on the outer periphery, and the axial direction of the preliminary gear W3 in which the helical tooth portion 21 is formed on the outer periphery. 3. A forging method for helical gears according to claim 1, further comprising: a second molding step of pressing an end surface of one end side 12 a with a punch 63 disposed on an inner periphery of the die 73.   The helical gear includes a first tooth portion 23 on which a helical tooth portion 21 is formed, and a second large diameter portion 22 that is continuous from the first tooth portion 23 and has a larger diameter than the outer diameter of the first tooth portion 23. 4. The forging method for a helical gear according to claim 1, wherein the helical gear W4 provided is forged.

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